The Duchy of Parma was a fief of the
Papal State. In 1639, Duke Odoardo Farnese (since 1622) was induced to ban the export of grain
from Parma territory (from the city of Castro) to the Papal State.

B.) The War

Pope Urban requested Spanish aid; Spain, involved in the 30 Years War (against the Dutch Republic and France) and facing rebellions
in Portugal and Catalonia, could do little to support the pope. The pope raised a force and occupied the Duchy in 1641. Odoardo Farnese
was supported by the Republic of Venice,
Modena and
Tuscany. In 1642, Urban VIII. excommunicated Farnese and cancelled his fiefs;
now Duke Odoardo invaded the Papal State. Attempts to negotiate a peace at Orvieto (1642) failed; in 1643 hostilities were resumed, without any
side achieving a victory. In 1644 the peace of Ferrara was concluded, a diplomatic victory for Duke Odoardo and humiliating for Pope Urban VIII.,
who had to lift the ban on Duke Odoardo and restore to him the Duchy of Parma.

C.) The Legacy

Pope Urban VIII. died in 1644, Duke Odoardo in 1646. In 1649, Pope Innocent had Castro occupied and razed to the ground. His successors
were to realize that the papacy was no longer able to pursue an active military policy. The Duchy of Parma, nominally a fief of the pope, was
treated in international policy as an independent state.